1. Field of Invention
The present invention relates to cardiovascular surgery and, more particularly, to techniques for retraction and subsequent exclusion of the left atrial appendage.
2. Description of the Prior Art
Embolic stroke is a major cause of disability and death. The most common cause of embolic stroke emanating from the heart is thrombus formation due to atrial fibrillation. Atrial fibrillation is an arrhythmia of the heart that results in a rapid and chaotic heartbeat that produces lower cardiac output and irregular and turbulent blood flow in the vascular system. There are over five million people worldwide with atrial fibrillation, with about four hundred thousand new cases reported each year. Atrial fibrillation is associated with a 500 percent greater risk of stroke due to the condition. A patient with atrial fibrillation typically has a significantly decreased quality of life due, in large part, to the fear of a stroke, and the pharmaceutical regimen necessary to reduce that risk.
For patients who have atrial fibrillation and develop atrial thrombus therefrom, the clot normally occurs in the left atrial appendage (LAA) of the heart. The LAA is a cavity that is connected to the lateral wall of the left atrium between the mitral valve and the root of the left pulmonary vein. The LAA normally contracts with the rest of the left atrium during a normal heart cycle, thus keeping blood from becoming stagnant therein. However, the LAA, like the rest of the left atrium, does not contract in patients experiencing atrial fibrillation due to the discoordinate electrical signals associated with atrial fibrillation. As a result, thrombus formation is predisposed to form in the stagnant blood within the LAA. Of the patients with atrial thrombus, a large majority have the atrial thrombus located within the LAA. The foregoing suggests that the elimination or containment of the thrombus formed within the LAA of patients with atrial fibrillation would significantly reduce the incidence of stroke in those patients.
Pharmacological therapies for stroke prevention such as oral or systemic administration of blood thinning agents, such as warfarin, coumadin or the like have been inadequate due to serious side effects of the medications (e.g. an increased risk of bleeding) and lack of patient compliance in taking the medication.
As an alternative to drug therapy, invasive surgical procedures for closing or altering the LAA have been proposed. For example, U.S. Pat. No. 6,652,555 discloses a barrier device in the form of a membrane for covering the ostium of the LAA to prevent blood clots in the LAA from escaping and entering the blood stream. Published U.S. Patent Application No. 2005/0004652 discloses an occlusion device for inhibiting compression of the LAA in which tissue in-growth onto the occlusion member is provided. Both of these devices are extremely invasive in that the LAA must be opened (usually during the course of open heart surgery) and a foreign device implanted therein. The implanting process itself is time consuming to perform and increases the risk of hemorrhage and infection.
Another approach has been to attempt to close the LAA by means of an externally applied device or instrument. For example, U.S. Pat. No. 6,488,689 discloses that closure of the LAA can be accomplished by a loop of material, such as a suture, wire, tape, mesh, or the like, which can be applied over the LAA and cinched in place to close the LAA. The '689 patent also discloses that closure can be accomplished by stapling, clipping, fusing, gluing, clamping, riveting, or the like. Published U.S. Patent Application Nos. 2005/0149068 and 2005/0149069 disclose several types of clamps that can be fitted about the LAA externally and the compressed against the LAA.
The Left Atrial Appendage Exclusion Patent discloses an externally applied exclusion device for the LAA that is easy to apply. The device in question will apply the proper amount of compressive force to exclude the LAA while minimizing or avoiding any stress concentrations that would lead to undesired tissue necrosis. Moreover, the device will avoid punctures that would lead to difficult-to-control bleeding.
Although externally applied devices and techniques, particularly those disclosed in the Left Atrial Appendage Exclusion Patent, offer a relatively simple and effective approach to the problem of excluding the LAA, a particular problem has not been addressed. This problem relates to properly grasping and positioning the LAA so that a suitable exclusion device can be applied thereto. Typically, a surgical assistant manually grasps the LAA and pulls outwardly. The LAA will be slightly stretched so that the exclusion device can be applied by the surgeon. A significant problem with this approach is that the LAA usually is very slippery due to the tactile qualities of its surface and due to the presence of fluids such as blood. This makes it quite difficult for the surgical assistant to grasp the LAA and maintain a proper grip. In addition, because the operating theater is quite small, the presence of the surgical assistant's hand means that the surgeon's access to the LAA is impeded. Impeded access to the LAA makes it more difficult and time-consuming for the surgeon to properly apply the exclusion device to the LAA.
Desirably, a technique would be available that would permit the LAA to be grasped readily. Preferably, any such technique would enable the LAA to be grasped firmly and retracted to any position desired by the surgeon while providing minimal interference with the surgeon's access to the LAA.